1. Field of the Invention
The present invention relates to a radiation imaging panel suitable for application to a radiation imaging apparatus using X-rays and the like and, specifically, relates to a method for manufacturing a photoconductive layer that constitutes the radiation imaging panel.
2. Description of the Related Art
Heretofore, in medical X-ray imaging, an X-ray imaging panel has been known, which uses a photoconductive layer sensitive to X-rays as a photosensitive member for the purpose of reducing a dose of radiation to which a subject is exposed, improving diagnostic performance, and so on. The X-ray imaging panel reads an electrostatic latent image formed on the photoconductive layer by the X-rays by means of light or a large number of electrodes, and records the image thus read. A method using the X-ray imaging panel is superior in that resolution thereof is higher than indirect radiography by a television camera tube, which is a well-known imaging method.
The above-described X-ray imaging panel is constituted to generate charges corresponding to X-ray energy by irradiating a charge generation layer provided therein with X-rays, and to read the generated charges as electric signals. The above-described photoconductive layer acts as the charge generation layer.
Heretofore, as a method for manufacturing the photoconductive layer, a vacuum evaporation method, a coating method and a single crystal method have been widely and commonly known. A photoconductive layer manufactured by the vacuum evaporation method is highly sensitive (for example, refer to U.S. Pat. Nos. 6,774,385 and 6,512,233). The coating method is superior in terms of manufacturing costs (for example, refer to Japanese Unexamined Patent Publication No. 2000-249769). A photoconductive layer manufactured by the single crystal method is superior in sensitivity, as in the vacuum evaporation method.
However, though such high sensitivity can be realized, the photoconductive layer manufactured by the vacuum evaporation method has problems that the manufacturing cost thereof is high, and that it is not necessarily possible to manufacture the photoconductive layer itself to have a desired composition, depending on the type of a material constituting the photoconductive layer, for example, a complex oxide. Meanwhile, though being superior in terms of the manufacturing costs, the photoconductive layer manufactured by the coating method has problems that image granularity is poor and sensitivity is low because the movement of the generated charges is inhibited owing to a binder, and because electric noise is increased. Moreover, in the single crystal method, the manufacturing costs of the photoconductive layer are high, and further, enlargement of an area thereof for the purpose of putting the photoconductive layer into practical use is technically difficult, and accordingly, the single crystal method is unsuitable for practical use.